System and method for production of electromagnetic waves



2,250,934 ETIC WA'VES R. S. OHL

SYSTEM AND METHOD FOR PRODUCTION OF ELECTROMAGN F iled June 14, 19:59

, INVENTOR R. S. OHL

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ATTORNEY Patented .July 29, 1941 UNiTEo- STATES PATENT. or ies SYSTEMAND METHOD FOR PRODUCTION" OF ELECTROMAGNETIC WAVES Russell S. 0111,Little Silver, N. J., assignor to Bell Telephone Laboratories,Incorporated, New York, N. Y, a; corporation of. New York.

Applicationlune l i, 1939,-Serial No. 279,063

11 Claims. (Cl.l17844) This invention relates to systems forproductionof electromagnetic waves and, more particularly, to systems inwhich the group wave energy from spark discharge sources isredistributed more uniformly with respect to time;

An object of the invention is to increasethe' power available from sparkdischarge oscillation systems.

An additional object of the invention is to provide substantiallycontinuous waves in the millimeter wave-length range.

An additional object is to insure that initiation of an individual groupof waves generated by a spark discharge oscillator is so timedthat theindividual waves of a group are correctly phased with respect to theindividual waves of Inaccordance with the invention, part of the Waveenergy of a discharge gap oscillator which produces intermittentgroupsof waves separated by blank intervals is radiated in a desireddirection. Another part of the energy from the same groups of wavesradiated in'a different direction impinges upon a reflector sopositioned with respect to the radiator that the reflectedenergy isreturned toward the radiator'in-the desired direction of propagation.The length of the'path' from the radiator to the reflector is such thatthe reflected waves arrive at the radiator at a time when the radiatoris inactive, thus tending to fill in the blank or inactive period. Ifthe reflected wave excites the radiator into oscillation and theoscillation continues until about the time when a new discharge is dueto occur;

the oscillation voltage in conjunction with the impulse applied to thegap to produce a' discharge may initiate or trigger off the newdischarge, thus causing the train of waves resulting therefrom to havecorrect phasing with respect to oscillations of the preceding group. Inorder to enable the discharge gap to have sufficient inactive time toinsure that there beno undue heating orpitting of the gap or excessiveionization of the atmospheric medium in its vicinity, additional gapsmay be associated with a common transmission medium and they may bearranged to operate sequentially so that each may rest while another-isactive. The'directly radiated waves and the reflected-waves may beintroduced into a network or complex pathhaving aplurality of paths ofindividually different transmission time lengths such that wave energydivided between the paths is more evenly distributed with respect totime as it emerges from the network.

In the drawing, 7

Fig. 1 illustrates schematically a spark gap discharge oscillator with areflector system for improving the distribution of wave energy withrespect to time.

Fig. 2 is a diagram to assist in explainingthe operation of the systemof Fig. 1.

Fig.- 3 illustrates a short wave system of the type shown in Fig. 1including a transmission path for redistributing energy of periodicgroups of waves with respect to time.

Fig. 4 shows a mesh ornetwork having a plurality of separate paths forconverting separate trains of high frequency waves into more evenlydistributed wave energy, and

Fig. 5 shows a portion of a transmission system embodying a plurality ofspark discharge oscillatorsso related asto cooperate in the transmis--sion' of increased high frequency wave energy.-

Referring specifically to Fig. 1, a spark gap discharge device I ismounted within a tube 2- of electrically conducting material andis'connect-ed in circuit with a high frequency choke coil 3 and a source4 of discharge electromotive force. connections 5- and 6.

passingthrough the insulator I and the metallic sleeve element 8. Theelectrodes of the'spark discharge device I, together with the section oftubel, may constitute an oscillation frequencydetermining circuit foroscillations of extremely highfrequency as, for example, of wave-lengthsof a few millimeters. The high frequency choke coil 3 permitsalternating electromotive forceshaving frequencies of the order of 100megacycles to be applied by source 4 to the discharge gap I but preventsescape of the millimeter wavelength energy by the same path. Theelectric discharge oscillator including the electrodes ofgapl may bedesigned as explained in my'-co pending application Serial No. 280,044,filed June 20, 1939 to serve as a linear radiator. Energy of themillimeter Wave-length will accordingly be radiated toward the left asindicated by the arrow A and toward theright as indicated by the arrowA. is closed-by a slidable reflector 9-which is adjustable to anydesireddistance with respect to the The circuit is completed by theground Electrical connections-to the discharge gap are eifectedby-lead-in wires The right-hand end of thetube' the travel time ofelectromagnetic wave energyfrom the gap I to the reflector 9 is 75/4.Wave energy radiated in the direction of A will accordingly be incidentupon the reflector 9 at an instant occurring t/{l after its. initialradiation from the source I. It will be reflected by reflector 9 in thedirection of the broken line arrow B and the reflected energy willarrive at the plane of the discharge gap at a time 13/2 after its.

initial radiation. It will be apparent therefore that the reflectingsystem enables the directly radiated energy A and the reflected energy Bboth to be propagated in the desired direction toward the left at timeswhich are separated by a half of the period between successive wavetrains.

Fig. 2 illustrates the condition in which the trains A and C of directlyradiated waves are intermingled with the intervening reflected wavegroups or wave trains B and D. It is, of course,

obvious that the reflector 9 might be placed closer to the gap I inwhich case the reflected wave trains B and D would approach more nearlythe direct trains A and C, respectively. On the other hand, thereflector 9 might be placed at a somewhat greater distance from thedischarge gap I so that each reflected wave train would be somewhat moreclosely adjacent to the succeeding directly radiated wave train. If, forexample, the reflector 9 be placed suificiently far from the gap I thereflected wave train B may arrive at the gap I at an instant which isjust prior to the initiation of the train C. With the proper adjustmentof the apparatus it will be possible to utilize the reflected waves toexcite the gap I to a degree which is suflicient in conjunction with theelectromotive force of the source 4 to trigger off the discharge for thewave train C. Under these circiunstances, phasing of the individualwaves of the direct train C may be controlled by the phasing of thewaves of the reflected train B thus enabling each train to fix thephasing of the individual waves of the succeeding train.

Fig. 3 illustrates a system which may employ the identical spark gaposcillator and reflector of Fig. 1. The tube 2 is extended to the leftto constitute a wave transmission path for additional redistribution ofthe energy of the spaced wave trains. For this purpose the tube isprovided with lateral chambers I I, I2 and I3 each with its individuallyadjustable reflector I4, I5 and I6, respectively. Wave trains of theform illustrated in Fig. 2 in their propagation to the left in the tube2 successively pass the reflecting chambers II, I2 and I3. At thejunction point of chamber II with the tube 2 a partial reflector I isprovided. The reflector may comprise a half wave-length radiatorinclined at 45 degrees to the direction of wave propagation or asimilarly inclined partially silvered mirror or sheet of dielectricmaterial. The energy of a wave train traveling along the tube is,accordingly, divided and a small portion of it proceeds downwardly inthe chamber I I and is reflected by the reflector I4 with a delayequivalent to twice the time required for electromagnetic waves totraverse the length of the chamber. If, for example, the chamber ll beadjusted, as illustrated, to have a length measured in propagation timeequivalent to t/32 the reflected energy will arrive back in the tube 2at an interval t/l6 after the directly propagated energy has passed thatpoint. Similarly, a portion of each wave train passing chamber I2 willbe delayed by an interval 15/8 and a portion of the energy passingthrough chamber I3 by an interval t/4. It will be apparent, therefore,that the effect of each of the reflecting chambers is to add a new wavetrain at the expense of energy of each wave train that passes it. Itfollows that the energy emitted at the opening I8 of the tube 2 Will beso redistributed as to simulate a continuous wave. Not only does thispermit the production of substantially continuous waves of wave-lengthsbeyond those readily attainable by electron discharge devices of thetype commonly employed, but it also greatly increases the power whichmay be transmitted by-discharge gap systems. This is for the reason thatextremely high potential gradients may be applied to an electricdischarge gap if the gap be given a sufliciently long inactive periodfollowing the discharge to permit tendencies toward excessive ionizationto subside. The system disclosed enables the discharge gapto rest duringthe intervals between discharges fora sufliciently long time to behighly effective when the next discharge is due to occur.

Fig.4 discloses an alternative to the reflector chamber system of Fig.3. The discharge gap and its reflector 9 are not illustrated in thisfigure but it will be understood that they are identical in characterwith those of Fig. 3 andare to be associated with the wave transmissionpath of Fig. 4 in the same manner as is the reflecting chamber system ofFig. 3. The energy from the discharge oscillator and reflector systemproceeding in the direction indicated by the arrow E will divide asindicated by arrows F and G. The wave train represented by arrow Ftransverses the longer path and will therefore experience a phase shiftor delay with respect to that of the wave train G. Similarly, at thenext junction point there is a division between Wave trains H andI, thelatter taking the longer path. It will be readily apparent that when allthese wave trains reunite as indicated at K those which have proceededby the direct paths will be followed by those which have taken thelonger paths. Accordingly, a redistribution of the energy will haveoccurred in which the initial groups A and C of directly radiated waveshave been divested'of a considerable portion of their energy to formintervening groups of Waves or wave trains which serve to substantiallyfill up the time between the original groups.

Fig. 5 illustrates a system similar to that of Fig. 3 in which two sparkdischarge gaps I9 and 29 each having. its own oscillation generatingsystem and both the systems designed to operate at the same frequencyare associated with a common energy transmission and redistributionsystem. The discharge gaps are each supplied with energy from anindividual source 2!, 22 connected in the plate circuit of triodes 23and 24, respectively. -The triodes 23 and 24 have their grid cathodecircuits connected in parallel to an impulsing source 25 correspondingin frequency and wave-form to the source 4 of Figs. 1 and 3 intervalsthe breakdown voltageof the gaps l9 and 20 and, accordingly, one or moredischarges, each with its train of oscillations, will be generated at agap during the impulse. In order-to permit one gap to rest while theother isoperating a switching source 28, which may be of -a very muchlower order of frequency, is connected to impress an electromotive forcedifferentially upon the input-circuits of the triodes so thatone triodeis effectively paralyzed while the other is active. The proportioning ofthe electromotive forces of the sources 25 and 26 to accomplish this inconjunction with the normal grid bias sources 21 and 28 will be obviousto those skilled in the art of electron discharge devices. It will onlybe necessary that during one-half cycle of the source 26 the net gridcircuit electromotive force is sufiicient to enable a breakdownelectromotive force to be applied by source 2| to gap I9 while, at thesame time, the net grid circuit electromotive force of the device 24prevents application of a breakdown potential to gap 20 by source 22.Preferably the source 26 is of a type generating square-topped waves sothat the switching action takes place so rapidly as not to introducesubstantial intervals of simultaneous inactivity of the two dischargegaps. Each gap is provided with its individual reflector 29 and 30.Inasmuch as the two gaps I9 and 2G operate sequentially and eachdischarge gives rise to many trains of waves by virtue of the action ofthe reflectors 29 and 30 and of the reflecting chambers 32, 33, 34 and35 associated with the transmission path 2, the energy emerging from theopen end of the transmission path 2 may closely simulate a continuousWave even though the individual gaps l9 and 20 each be inactive forconsiderable periods between discharges.

Although certain preferred embodiments of the invention have been shownand described it will be noted that various modifications and changesmay be made therein within the scope of the appended claims withoutdeparting from the spirit of the invention.

What is claimed is:

1. In combination, an electric discharge gap, a source of periodicelectromotive force connected in circuit therewith of sufiicient peakelectromotive force to exceed the breakdown potential of the gap, thegap having electrodes to serve as radiating elements and constituting asource of discrete electromagnetic wave trains, and a reflectorassociated with the gap and spaced therefrom a distance substantiallyequal to that over which a wave train may be propagated during a quarterof the period between successive discharges across the gap.

2. The combination of a wave generation system comprising a source oftrains of high frequency oscillations which trains are separated bysubstantially blank intervals, with a wave transmission systemassociated with the source and disposed to receive wave energy therefromand to guide it to a remote point, the transmission system comprising aplurality of paths whose lengths correspond to different transmissiontimes, the difierence in lengths of two of the paths being such thatwhen a given wave train is transmitted to the remote point over bothpaths that portion arriving over the longer path arrives at the pointduring the otherwise blank interval succeeding the arrival ofthe:portion arriving overthes'horterpoint.

3. In combination, annelectric discharge gap, *a-source of.electromotiveforce connected in circuit therewith: to periodicallyimpress anelectromotive force in excess of the breakdown voltage -=ofthe gap, anoscillatory system connected to the gap whereby 'trains ofwaves are produced with a'train periodicity corresponding to that of thedischarges across .the gap and a wave frequency corresponding to thenatural frequency of the oscillatory system,- andmeansincluding arezflector'associated with the gap to redistribute the -wave' trainenergy after its generation with-respect to time so'asto cause it to bepropagated more nearly in the manner of continuous waves.

4. In combination, an electric discharge gap, means for producingdischarges thereacross at periodic intervals to set up a train ofoscillations at each discharge and a wave transmission system coupled inenergy receiving relation thereto, the system including means fordividing the energy of each train of oscillations into a plurality ofportions and delaying some of said portions with respect to others todistribute the total energy of each train more evenly with respect totime.

5. The method of wave propagation which comprises generating periodicgroups of oscillations separated by voids, subjecting the groups ofoscillations to an energy division, and delaying difierent parts of thedivided energy differently to fill in portions of the voids wherebyeffectively continuous waves are produced.

6. In combination, a source of high frequency oscillations capable ofproducing intermittent wave trains of oscillations of a predeterminedfrequency separated by blank intervals, means for radiating the wavetrains in a plurality of directions including a desired direction ofpropagation and means for intercepting energy radiated in a directionother than a desired direction and for reradiating it in the desireddirection in the blank intervals.

7. A radio transmission system comprising a source of intermittenttrains of waves with intervening time intervals, means connected theretofor radiating a portion of the energy of the wave trains in a desireddirection, and means for delaying substantially all of the remainingenergy of the wave trains and for radiating it in the desired directionduring the intervening time intervals.

8. A short wave system comprising a plurality of sources of intermittenttrains of waves of like frequency, means for energizing each of saidsources, means coupling said sources together in a manner to effectparalysis of each source during periods of activity of any other source,and a transmission path coupled in energy transfer relation to each ofsaid sources so as to be excited by one source during the paralysis ofanother and thus to transmit a more uniform flow of energy.

9. The method of generating and transmitting high frequency energy whichcomprises producing a series of pulses of oscillations of a givenfrequency, the pulses occurring at a definite periodicity, suppressingproduction of oscillations of the pulse series for definite timeintervals between the pulses to permit conditions of osci lationproduction to return to normal, producing another series of pulses ofoscillations of the same frequency during the time intervals between thepulses of the first series and transmitting oscillations from bothseries over a common path to effect a more nearly uniform flow ofoscillation energy than would be afforded by either of the individualseries of pulses.

10. The method of generating and transmitting high frequency energywhich comprises producing a first periodic sequence of energy pulses ata certain frequency, separated by blank intervals, deriving from saidfirst sequence a second periodic sequence of like pulses at the samefrequency but delayed with respect to pulses of said first sequence byone half of the pulse period, and transmitting pulses of said derivedsequence and said original sequence in suc- 15 cession over the samepath.

11. The method. of generating and transmitting high frequency energywhich comprises producing a primary periodic sequence of energy pulsesat a certain frequency, separated by blank intervals, deriving from saidfirst sequence a plurality of secondary periodic sequences at the samefrequency, delaying pulses of each of said secondary sequences byunequal fractions of a period with respect to corresponding pulses ofsaid primary sequence, so as substantially to fill the blank intervalsof the primary sequence with pulses of the derived sequences, andtransmitting the pulses of all of said sequences together.

RUSSELL S. OHL.

